1. Field of the Invention
The present invention relates to an Internet telephone apparatus for connecting an Integrated Service Digital Network (ISDN) to an Internet network in an internet telephone system which replaces a portion of communication services utilizing a public line such as a telephone call, facsimile (FAX) transmission, and so on with communication services through the Internet network.
2. Description of Related Art
In recent years, the Internet telephone system has been developed, taking advantage of the Internet, and ITU-T (International Telecommunication Union-Telecommunication Standardization Sector) has also rounded off international recommendations for the Internet telephone system, and communications of images, voice, data and so on, utilizing the Internet.
In the following, a conventional Internet telephone system and a conventional Internet telephone apparatus will be described with reference to the accompanying drawings.
FIG. 1 illustrates the configuration of a conventional Internet telephone system.
Referring specifically to FIG. 1, the Internet telephone system comprises telephones 7, 8 of users who may utilize Internet telephones; an Internet network 4; Integrated Service Digital Networks (ISDN) 5, 6; Internet telephone apparatus 21, 22 for converting a normal telephone communication to an Internet telephone communication; an Internet telephone control center 3 dedicated to management and connection/disconnection control for Internet telephone apparatus located in respective areas; personal computers 11, 12 of users for utilizing the Internet for purposes of personal computer communications or the like; and access servers 9, 10 for providing dial-up IP connections to the personal computer 11 and the personal computer 12, respectively.
FIG. 2 illustrates a functional block diagram of the conventional Internet telephone apparatus 21 or 22.
Referring specifically to FIG. 2, the Internet telephone apparatus 21 or 22 comprises a Layer 1 control unit 42 for performing the control related to Layer 1; a Layer 2 control unit 43 for performing the control related to Layer 2; and a Layer 3 control unit 44 for performing the control related to Layer 3, each of which controls a connection of the Internet telephone apparatus 21 or 22 with the ISDN 5 or 6. Here, a layer refers to a layer in the seven-layer model of the open system interconnection (OSI), wherein Layer 1 refers to a physical layer for defining the communication rate, transmission scheme, transmission codes, and so on; Layer 2 to a data link layer for performing the formation of signal units, detection of transmission errors, retransmission control, flow control on a signal data link, and so on; and Layer 3 to a network layer for performing signal message routing, distribution of signal messages, selection and release of a communication path, and so on. In the ISDN, the control related to Layer 1 is defined by ITU-T Recommendations I.430, I.431, and so on; the control related to Layer 2 is defined by ITU-T Recommendations Q.920, Q.921, and so on; and the control related to Layer 3 is defined by ITU-T Recommendations Q.930, Q.931, and so on. An internet telephone control unit 45 in the Internet telephone apparatus 21 or 22 is provided for compress/decompress of a voice (audio) signal transmitted thereto from a telephone through the ISDN 6, connection/disconnection and control for the Internet telephone control center 3 or another Internet telephone apparatus through the Internet network, and so on. A system control unit 41 generally controls the Layer 1 control unit 42, the Layer 2 control unit 43, the Layer 3 control unit 44, and the Internet telephone control unit 45.
FIG. 3 shows signal scheme specifications for a frame format in the ISDN.
In FIG. 3, a flag sequence is an information element added before and after a frame for identifying the frame; an address field is an information element for identifying a Layer 2 link as well as for identifying whether the frame is a command (for instructing the destination to execute a particular function) or a response (for reporting an executed operation and the state after the execution with respect to one or a plurality of commands); a control field is an information element used to transfer the type of a command or a response and a sequence number for executing information transfer and monitoring functions as well as a control function on a Layer 2 link; an information field is an information element for setting therein information to be actually transferred; and a frame check sequence is an information element for setting therein redundancy data for checking errors in the frame. The Layer 2 control unit 43 performs control for commands and responses based on information in the address field and the control field, as well as perform control for error detection, repetitive request for information, and so on based on information in the frame check sequence. The Layer 3 control unit performs routing of a signal message, distribution of a signal message, selection and release of a communication path, and so on based on information in the information field.
For transferring a frame, the flag sequence, the address field, the control field, the information field, the frame check sequence, and the flag sequence are sequentially sent in this order from the top octet to the lowest octet. Upon originating a call, information elements related to a call setting message including a call number information element, a destination number information element, a transmission capability information element, a source sub-address information element, a destination sub-address information element, a lower layer alignment information element, a user-to-user information element, and so on are set in the information field. Here, the call number information element includes an information element for identifying an individual call when a plurality of calls are simultaneously handled; the destination number information element includes an information element indicative of a telephone number of the destination side; the transmission capability information element includes an information element for identifying whether an associated call is a voice communication or a digital (data) communication; the source sub-address information element includes an information element indicative of a sub-address number on the source side (a sub-address number for identifying the source of a call within a plurality of terminals connected to a single ISDN line); the destination sub-address information element includes an information element indicative of a sub-address number on the destination side (a sub-address number for identifying the destination of a call within a plurality of terminals connected to a single ISDN line, as opposed to the source sub-address); the lower layer alignment information element includes an information element for notifying detailed information on a voice encoding scheme, data protocol, and so on; and the user-to-user information element includes an information element used to communication information between users. The transmission capability information element further includes information elements such as information transfer rate (from the destination to the source) information element; a user information Layer 1 protocol information element; a user rate information element; and so on, while the lower layer alignment information element further includes information elements such as an information transfer rate (from the destination to the source) information element, a Layer 1 protocol identification information element; a user rate information element; and so on.
Now, the operation of the conventional Internet telephone apparatus is described with reference to FIGS. 1 to 3. When the users speak between the telephone 7 and the telephone 8, a call is originated from the originating telephone 7 to the Internet telephone apparatus 21 through the ISDN 5, and the Internet telephone apparatus 21 responds to the call to enter a telephone communication state utilizing the ISDN 5.
In this event, the information field including information elements related to a call setting message such as the destination number information element, the transmission capability information element, the source sub-address information element, the destination sub-address information element, the lower layer alignment information element, the user-to-user information element and so on, defined by the frame format as illustrated in FIG. 3, is transferred to the Internet telephone apparatus 21 through the ISDN 5.
Next, the Internet telephone apparatus 21 prompts the user of the telephone 7 to input an authentication number, the telephone number of the destination, and so on through voice guidance. With the authentication number and the telephone number of the destination transmitted from the telephone 7, the Internet telephone apparatus 21 confirms the authentication number of the user in the Internet telephone control center 3 through the Internet network 4, and then performs a connection control, including the passing of the destination telephone number, and so on, with the Internet telephone apparatus 22. The Internet telephone apparatus 22 originates a call to the called telephone 8, with the received destination telephone number, through the ISDN 6. When the user of the telephone 8 hooks off, a telephone communication state is entered between the Internet telephone apparatus 22 and the telephone 8 through the ISDN 6. Subsequently, voice signals from the telephones 7, 8 are compressed/decompressed by voice compress/decompress devices in the Internet telephone apparatus 21, 22, so that compressed voice data is transmitted and received between the Internet telephone apparatus 21, 22 through the Internet network 4, whereby the user of the telephone 7 can speak over the telephone with the user of the telephone 8.
In the conventional Internet telephone apparatus, however, when an Internet telephone service provider (hereinafter, referred to as the xe2x80x9cITSPxe2x80x9d) for providing users with accesses to an Internet network provides the Internet telephone service, another line must be installed exclusively for an Internet telephone apparatus in addition to a public line for an access server, thereby presenting a problem of requiring a cost for additionally installing a line and an extra expense for maintenance of the newly installed line. In addition, a dedicated line must be always reserved exclusively for the Internet telephone in spite of the fact that the frequency of accesses from users largely varies depending on time zones, thereby implying a problem that the line cannot be efficiently utilized.
The present invention has been made to solve the problems inherent to the prior art, and its object is to provide an Internet telephone apparatus which is capable of Internet connection processing both for an Internet telephone service and for a personal computer communication service through a single telephone line by switching the line between an Internet telephone control unit and an access server, upon receiving an incoming call, thereby achieving an efficient utilization of a telephone line through switching and sharing of the telephone line.